VB.NET Convert USB as RS232 - vb.net

Question

I have a hardware with USB for communicate between computer to hardware. The vendor not giving any APIs to connect to the device. They give me a protocol. But the protocol is serve for RS232 mode. I ask the vendor whether this protocol can be apply to the USB, they said 'YES'.. So, I'm thirst of idea how to use this protocol. Does anyone know? My old friend said yes I can use the USB and treat is as COM which I need to create an object. Create instance of the object which declare as a serialport as below. But it still can't get the status.
Public Sub New(ByVal intComNumber As Integer, ByVal lngBaudRate As Long, ByVal intDataLng As Integer, ByVal intStopBit As Integer, ByVal intParity As Integer)
Try
objUPSPort = New SerialPort
With objUPSPort
.PortName = ("COM" & intComNumber)
.BaudRate = lngBaudRate
.DataBits = intDataLng
.StopBits = intStopBit
.Parity = intParity
.Handshake = Handshake.None
End With
Catch ex As Exception
MsgBox("Error In Init UPSComm")
End Try
End Sub
Can someone help me identified this? This hardware is UPS. A simple command write to the port. But I get the error when get status. Below is the code to write to the UPS.
Public Function GetStatus() As String
Dim strRet As String
Dim strRecv As String
Dim byteRead() As Byte
Try
If Not IsNothing(objUPSPort) Then
objUPSPort.Open()
objUPSPort.WriteLine("Command will be here" & vbCrLf)
For i = 0 To 100000
If objUPSPort.BytesToRead >= 45 Then
Exit For
End If
Next
ReDim byteRead(objUPSPort.BytesToRead)
objUPSPort.Read(byteRead, 0, objUPSPort.BytesToRead)
strRecv = String.Empty
For i = 0 To byteRead.Length - 1
strRecv = strRecv & Chr(byteRead(i))
Next
If byteRead(38) = 48 Then
MsgBox("Power OK")
ElseIf byteRead(38) = 49 Then
MsgBox("Power Off")
Else
MsgBox("Unknown")
End If
strRet = strRecv
Return strRecv
Else
MsgBox("Error In ComPort Object")
Return String.Empty
End If
Catch ex As Exception
MsgBox("Exception In ComPort Object - " & ex.Message)
Return String.Empty
Finally
objUPSPort.Close()
End Try
End Function

Answer 1

I had few experiences in RS232 comm with USB, as nowadays laptops/pc they dont come with serial port no more. Serial ports usually emulated by USB, using [TTL-to-RS232 transistor, MAX like] some common supplier would use prolific as driver to emulate USB-to-RS232. First you need to know the data type, a simple string or binary.
SerialPorts is event driven, data coming thru the ports can trigger events. I assume to get UPS to send you status, first, you need to send command, as such [some pseudo];
objUPSPort.WriteLine("Command will be here" & vbCrLf)
There two ways to get the data:
Using data receive event driven :
Private Sub objUPSPort_DataReceived(sender As Object, e As IO.Ports.SerialDataReceivedEventArgs) Handles objUPSPort.DataReceived
'call ReceiveData()
End Sub
Create a pooling thread to read data periodically
Private Sub threadUPSReceive()
Do
data = objUPSPort.ReadLine() 'for string
'process the data here or call ReceiveData()
Loop
End Sub
If data stream to be read is binary (similar like yours):
Private Function ReceiveData()
Dim bRead As Integer
Dim returnStr As String = vbEmpty
bRead = objUPSPort.BytesToRead 'Number of Bytes to read
Dim cData(bRead - 1) As Byte
For Each b As Byte In cData
returnStr += Chr(b) 'put data stream in readable ascii
Next
Return returnStr
End Sub
One more thing, make sure the baudrate/stopbit/databit is set correctly.
Hope this help.